Diameter gauge for machine tools

ABSTRACT

A diameter measuring gauge for machine tools comprising two opposed feelers both movable with respect to one another. The feelers are mounted on arms carried by sleeves that slide on a column. The arms are biased in so that the feelers contact the workpiece with the proper pressure. A hydraulic cylinder coupled to the arms drives the two arms until the feelers make initial contact with the workpiece, then the hydraulic pressure is removed. Measurement is accomplished by a pair of windings carried by the arms in juxtaposition to each other to electrically interact to produce an electrical signal proportional to the diameter of the workpiece.

Filed:

Appl. No.: 184,566

DIAMETER GAUGE FOR MACHINE TOOLS Inventors Elio Pagella; Carlo Guerici,both of lvrea, ltaly Assignee: Ing. C. Olivetti &C., S.p.A., Ivrea,

Turin, Italy Sept. 28, 1971 Foreign Application Priority Data 7 Sept.30, i970 .lta ly...,. ..70262 A/7 0 us. Cl 33/143 L, 33/147 E- Int. Cl.G0lb 5/00 Field of Search 33/143 R, 143 L,

33/147 R, 147 L,'l47 N, 147 E, 147 F, 147

H, 147 T, 147 K, D10. 2, 168 AB References Cited UNITED STATES PATENTS6/1972 l/l96l Frohling 33/143 L Etchell 33/147 E FOREIGN PATENTS ORAPPLICATIONS France 33 147 R [4 1 Jan. 1, 1974 Primary Examiner-WilliamD. Martin, Jr. Attorney-Birch, Swindler, McKie & Beckett 5 7 ABSTRACT Adiameter measuring gauge for machine tools comprising two opposedfeelers both movable with respect to one another. The feelers aremounted on arms carried by sleeves that slide on a column. The arms arebiased in so that the feelers contact the workpiece with the properpressure. A hydraulic cylinder coupled to the arms drives the two armsuntil the feelers make initial contact with the workpiece, then thehydraulic pressure is removed. Measurement is accomplished by a pair ofwindings carried by the arms in juxtaposition to each other toelectrically interact to produce an electrical signal proportional tothe diameter of the workpiece.

6 Claims, 3 Drawing Figures 1 DIAMETER GAUGE FOR MACHINE TOOLSBACKGROUND OF THE INVENTION The present invention relates to a diametergauge for machine tools comprising two feelers adapted to sense twodiametrically opposite points of a workpiece of cylindricalcross-section disposed on the machine tool.

Diameter gauges of the aforesaid type are known in which the two feelersare connected to two transducers of capacitive type or electromagnetictype. In these devices, the capacitance of a capacitor or the magneticflux linked with a winding is varied by theshifting of a movable elementwith respect to a fixed element. The capacitance or the flux gives themeasurement of the diameter as the difference, generally very small,from a sample calibration diameter of the device. If it is desired tomeasure a plurality of diameters on the part or workpiece, the diametergauges of the aforesaid type require a zeroizing or reset operation foreach required diameter and this is accomplished measuring a calibratedsample having the required diameter. This therefore makes it difficultto measure a plurality of diameters on the same part. Moreover, sincethese gauges supply the measuring unit of the machine only with anindication of the difference between the actual diameter and thetheoretical diameter, the actual diameter is ascertained only after somecalculations.

There are also known absolute gauges for diameters in which the twofeelers are carried by two arms disposed on the same side of theworkpiece and rotatable to approach the workpiece itself. After thisrotation, a feeler is first brought into Contact with the workpiece tobe measured and the other feeler is thereafter brought into themeasuring position. In one of these known absolute gauges, the sequenceof these movements is controlled by two microswitches actuated by thefeelers themselves during their movement. This gauge has thedisadvantages of being tricky to operate and of having a rather longtime of approach to the part.

In another of these known absolute gauges, the two feelers are shiftedsimultaneously by means of two opposed worms and nuts as far as a givenzero position. The measurement of the diameter of the workpiece iseffected as the difference between the distance between the feelers andthe distance from the feelers to the workpiece. These gauges have thedisadvantage that the measurement is not very precise, for which reasonthey are not usable for certain machining operations.

SUMMARY OF THE INVENTIONS the feelers for supplying an electrical signalindicative of the relative distance between the feelers, the feelersbeing carried by two opposite and parallel arms each j, extending from acorresponding sleeve connected resiliently to the correspondingfluodynamic device, the said sleeves being coaxial and guided slidablyone on the other.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described inmore detail, by way of example, with reference to the accompanyingdrawings, in which:

FIG. 1 is a longitudinal section of a diameter gauge embodying theinvention;

FIG. 2 is a section on the line II-Il of FIG. 1;

FIG. 3 is a section on the line III-Ill of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The diameter gauge embodying theinvention is adapted to measure the diameters of a part of workpiece ofcircular cross-section. More particularly, the gauge is adapted tomeasure the workpiece during machining to control, for example, the feedof the too]. To this end, the gauge may be fitted to the frame of themachine tool, which may be a lathe, a milling machine or a grinder.

Referring to FIG. l, a guide 5 is fixed to the frame of the machine anda slide 4 carrying the frame 6 of the diameter gauge is slidable on theguide 5. The guide is arranged transversely of a workpiece 3 which isbeing machined and is fixed in known manner to the machine. The gauge ismoreover disposed on the opposite side with respect to a tool 2, so asto supply the measurement of the actual diameter continuously during theworking cycle. The slide 4 is slidable on the guide 5 perpendicularly tothe workpiece, for example by means of a hydraulic device not shown inthe drawing, to allow the bringing up and moving away of the gauge atthe beginning and end of the measuring operation.

The gauge comprises two vertical feelers 7 and 8 carried by twohorizontal and parallel arms 9 and 10. The feelers 7 and 8 can slidevertically in the two arms 9 and 10 and are clamped in the latter bymeans of set screws 11 and 12.

The arm 9 is integral'with a block 13 of substantially rectangular form(FlG. 2) tapered towards the end adjacent the arm 9. The block 13 isfixed to a sleeve 14 (FIG. 1) slidable vertically on two rows of balls15 and 16 carried by a cage 17, which is also slidable vertically. Theballs 15 and 16 slide vertically on a shaft 18, the ends of which arefixed to the frame 6 of the gauge.

The diameter gauge comprises a position detector which is constituted bya slider element 19 and a scale element 34, movable vertically one withrespect to the other and substantially of the type described in UnitedStates Pat. No. 2,799,835. The slider element 19 is the detector, andcomprises a pair of multipolar primary windings (not shown in detail)which are offset so as to be spatially out of phase with one another andare in the form of printed circuits mounted on a board 45 of insulatingmaterial and fixed to the element 19. The ends of the windings areconnected to four terminals 46.

The scale element 34 comprises a multipolar secondary winding which isalso in the form of printed circuit (not shown in detail) on a board 47of insulating material fixed to the element 34. The ends of thesecondary winding are connected to two terminals 48.

The position detector is connected through the terminals 46 and 48 ofthe primary and secondary windings to an electronic apparatus not shownin the drawing, for example of the type described in our Italian Pat.No. 737,7l I. This apparatus comprises an analog-todigital converter,which enables the device to give from time to time a numerical value ofthe measurement effected. This apparatus moreover permits the resettingof the detector in a predetermined position and the visual display ofthe numerical values of the other positions in relation to thispredetermined position.

Connected to the element 19 is a shaped block 20 which bears a pin 21 atits upper end. Another pin 22 is fast with a hydraulic piston 23slidable in a cylinder 24 and normally arrests the pin 21 and,therefore, the blocks 13 and 20'and the element 19 are in opposition tothe action of a spring 25 (FIG. 3). This spring is attached by its upperend to a drilled pin 26 carried by a plate 50 fixed to the frame 6 ofthe gauge. The spring 25 is attached at its lower end to a pin 27 fastwith the block 13.

The arm 10 (FIG. 1) is integral with another block 28 of a form similarto that of the block 13 and fixed to a second sleeve 29. This sleeve isslidable vertically on two rows of balls 30 and 31 carried by cages 32and 33, respectively. Fixed to sleeve 29 is a pin 42 to which the lowerend of a spring 40 is attached. The upper end of the spring 40 isattached to another pin 41, which is drilled and carried by the plate50.

The balls 30 slide vertically on the shaft .18, while the balls 31 slidevertically on the surface of the sleeve 14. At the other end of theblock 28 is fixed the other eleq mentor scale 34 of the positiondetector, which is connected to a block 35 carrying a pin 36 at its freeend. Another pin 37 is fast with a second hydraulic piston 38 slidablein another cylinder 39 and normally arrests the pin 36 in opposition tothe action of the gravity of the blocks 28 and 35 and of the element 34.The spring 40 therefore has the function of partially counterbalancingthe weight of these components.

The delivery of the oil to the cylinders 24 and 39 and the discharge ofthe oil from them is effected through pipes, of which there are shown inFIGS. 1 and 2 and pipes 43 and 44 for inlet to the lower chambers of thecylinders. These pipes are connected to a hydraulic control unit, notshown in the drawing, in a manner known per se.

In operation, the workpiece 3 to be measured having been fixed, forexample between the centres of the machine tool oil under pressure issent through the appropriate pipes so that the piston 23 is urgeddownwardly and the piston 38 is urged upwardly. In consequence of this,the pin 22 pushes the pin 21 downwardly against the force of the spring25 and therefore pushes the arm 9 and the feeler 7 downwardly.Simultaneously, the piston 38 pushes the pin 36 upwardly through themedium of the pin 37. This causes the arm 10 and, consequently, thefeeler 8 to be shifted upwardly.

I By acting on the hydraulic control device for the slide 4, the slide 4is now moved towards the workpiece 3 so as to bring the two feelers 7and 8 into the vertical plane passing through the axis of the centresbetween which the workpiece 3 itself is fixed. To effect the bringing upof the feelers 7 and 8 up to the workpiece 3, the oil is now deliveredinto the lower part of the cylinder 24 and into the upper part of thecylinder 39. The piston 23 therefore moves upwardly and the piston 38downwardly. The pin 22 of the piston 23 thus leaves the pin 21, as aresult of which the spring 25 causes the sleeve 14 to slide on the shaft18 and shift the arm 9 upwardly. The feeler 7 is therefore brought intocontact with the workpiece 3. In turn, the pin 37 of the piston 38leaves the pin 36, as a result of which, through the effect of the forceof gravity, the sleeve 29 slides downwardly on the shaft 18 and on thesleeve 14, causing the arm 10 to move downwardly. The feeler 8 istherefore brought into contact with the workpiece 3. The springs 25 and40 are calibrated so that contact of the feelers 7 and 8 with theworkpiece 3 is ensured with a pressure such as not to introduce errorsinto the measurement. These errors in measurement may arise eitherbecause the feelers 7 and 8 do not maintain contact with, or follow, theworkpiece 3 perfectly owing to insufficient pressure or becauseexcessive pressure causes elastic deformations in the arms 9 and 10 andowing to the effect of possible rebounds and vibrations of the feelers 7and 8 on the workpiece.

In consequence of the position assumed by the feelers 7 and 8, the twoelements 19 and 34 constituting the position detector assume acorresponding relative position, which is detected by the relativeshifting between the secondary winding and the pair of primary windings.

In order to obtain the numerical value of the measurement of thediameters, the origin of the numerical values supplied by the electronicapparatus must correspond to a diameter of zero value detected by thediameter gauge or measuring device. To obtain this, it is necessary toeffect a calibration operation. To this end, a sample workpiece of knowndiameter is mounted on the machine tool and the measurement is effectedas described hereinbefore. In general, the electronic apparatus does notsupply the numerical value corresponding to the diameter of the sampleworkpiece, because the origin of the numerical values supplied is offsetby a certain value with respect to the zero diameter. As is known, theelectronic apparatus comprises zerosetting means for shifting the originof the numerical values supplied. By acting on these means, the resultof the measurement is varied until it is caused to coincide with theknown value of the sample diameter. This calibration operation iseffected at the beginning of a series of measurements and serves for allthe succeeding measurements. The calibration operation may, however, beeffected in any known manner, for example by means of calipers.

In FIG. 1, the two arms 9 and 10 are located substantially in theposition of maximum opening, so that the diameter of the workpiece 3shown in the drawings is substantially the maximum measurable. The rangeof the diameters measurable by the gauge corresponds substantially tothe vertical travel of the two arms 9 and 10. The minimum diametermeasurable is indicated in FIG. I by the dashed lines.

However, by changing the position of the feelers 7 and 8 with respect tothe arms 9 and 10 by means of the securing screws 11 and 12, it ispossible to translate this range of measurement to include substantiallythe maximum diameter, which is a little less than the maximum distancewhich can be reached by the arms 9 and 10. The range of measurement canalso be translated to include zero diameter.

It is therefore clear that the feelers 7 and 8 are movable in oppositedirections at the same time with a high degree of relative movement toprovide a high speed of approach of the feelers to the workpiece.

It is moreover clear that the diameter gauge is safe and reliable inoperation, since the movement of the feelers is not controlled bymicroswitches.

Other embodiments and modifications will become apparent to thoseskilled in the art from the above description, but it should beunderstood that the invenand having an inner surface overlying the outersurface of said other sleeve in telescopic relationship thereto, theother of said sleeves overlying the surface of said shaft,

fluodynamic means connected to each of said sleeves to move said sleevesrelative to one other, and electrical means connected to said sleevesfor sensing the position of one of said feelers with respect to theother of said feelers and generating an electrical signal indicativethereof.

2. A gauge according to claim 1 further comprisin first rolling bearingmeans disposed the length of said other sleeve for movably supportingsaid other sleeve on said shaft and second rolling bearing meansinterposed between said inner surface of said annular portion of saidone sleeve and said outer surface of said other sleeve.

3. A gauge according to claim 1 wherein said fluodynamic means comprisesa pair of hydraulic motors arranged in parallel to one another, saidhydraulic motors each being operatively counterconnected with said pairof sleeves for moving said sleeves in opposite directions, therebymoving said feelers relative to said workpiece.

4. A gauge according to claim 3 wherein said feelers, said arms and saidsleeves are in vertical alignment with one another, the upper one ofsaid sleeves being connected to its respective said hydraulic motorby-means of a one-way coupling allowing only upward motion to beimparted by said hydraulic motor and having a first tension springconnected between the frame of the ma chine tool and said upper sleeveto bias said upper sleeve upwardly with a predetermined force, the lowerone of said sleeves being connected to its respective hydraulic motor bymeans ofa one-way coupling allowing only downward motion to be impartedby said hydraulic motor and having a second tension spring connectedbetween the frame of said machine tool and said lower sleeve'to biassaid lower sleeve upwardly with a predetermined force, said upper feelercontacting the workpiece under the action of gravity partiallycounterbalanced by said first tension spring and said lower feelercontacting the workpiece under the action of said second tension spring,whereby said hydraulic motors drive said sleeves apart to allow theworkpiece to be interposed between said feelers.

5. A gauge according to claim 3 wherein said arms are parallel to oneanother.

6. A gauge as claimed in claim 1, wherein said electrical meanscomprises a first electrical winding mounted on a first board fixed toone of said sleeves and a second electrical winding mounted on a secondboard fixed to the other of said sleeves and spaced from said firstboard by an air gap and electrically coupled across said air gap to saidfirst winding, said boards being movable with said sleeves to alter theelectrical coupling across said gap thereby indicating the relativedisplacement of said sleeves.

1. A diameter measuring gauge for a machine tool comprising a pair ofopposed feelers for contacting opposed points of a workpiece each saidfeeler being mounted respectively on an arm, a pair of sleeves slidablerelative to one other, each of said sleeves supporting one of said arms,a shaft, substantially parallel to the plane of movement of saidfeelers, said sleeves being slidably and coaxially mounted on saidshaft, one of said sleeves including an annular portion spaced from saidshaft and having an inner surface overlying the outer surface of saidother sleeve in telescopic relationship thereto, the other of saidsleeves overlying the surface of said shaft, fluodynamic means connectedto each of said sleeves to move said sleeves relative to one other, andelectrical means connected to said sleeves for sensing the position ofone of said feelers with respect to the other of said feelers andgenerating an electrical signal indicative thereof.
 2. A gauge accordingto claim 1 further comprising first rolling bearing means disposed theleNgth of said other sleeve for movably supporting said other sleeve onsaid shaft and second rolling bearing means interposed between saidinner surface of said annular portion of said one sleeve and said outersurface of said other sleeve.
 3. A gauge according to claim 1 whereinsaid fluodynamic means comprises a pair of hydraulic motors arranged inparallel to one another, said hydraulic motors each being operativelycounterconnected with said pair of sleeves for moving said sleeves inopposite directions, thereby moving said feelers relative to saidworkpiece.
 4. A gauge according to claim 3 wherein said feelers, saidarms and said sleeves are in vertical alignment with one another, theupper one of said sleeves being connected to its respective saidhydraulic motor by means of a one-way coupling allowing only upwardmotion to be imparted by said hydraulic motor and having a first tensionspring connected between the frame of the machine tool and said uppersleeve to bias said upper sleeve upwardly with a predetermined force,the lower one of said sleeves being connected to its respectivehydraulic motor by means of a one-way coupling allowing only downwardmotion to be imparted by said hydraulic motor and having a secondtension spring connected between the frame of said machine tool and saidlower sleeve to bias said lower sleeve upwardly with a predeterminedforce, said upper feeler contacting the workpiece under the action ofgravity partially counterbalanced by said first tension spring and saidlower feeler contacting the workpiece under the action of said secondtension spring, whereby said hydraulic motors drive said sleeves apartto allow the workpiece to be interposed between said feelers.
 5. A gaugeaccording to claim 3 wherein said arms are parallel to one another.
 6. Agauge as claimed in claim 1, wherein said electrical means comprises afirst electrical winding mounted on a first board fixed to one of saidsleeves and a second electrical winding mounted on a second board fixedto the other of said sleeves and spaced from said first board by an airgap and electrically coupled across said air gap to said first winding,said boards being movable with said sleeves to alter the electricalcoupling across said gap thereby indicating the relative displacement ofsaid sleeves.